NOVELTY - A composition (C1) comprises (wt.%): a styrenic polymer (1-40 wt.%) selected from rubber-modified polystyrenes, unhydrogenated block copolymers of alkenyl aromatic compound and conjugated diene, and/or hydrogenated block copolymers of alkenyl aromatic compound and conjugated diene; flame retardant (1-40) comprising organophosphate ester; and poly(arylene ether)-polysiloxane block copolymer reaction product (greater than 55-95) comprising poly(arylene ether) homopolymer, and poly(arylene ether)-polysiloxane block copolymer.    USE - As composition useful for forming injection molded article e.g. photovoltaic junction box or a photovoltaic connector (claimed).    ADVANTAGE - The composition exhibits stiffness and a good balance of flame retardancy, impact strength, flow, and heat resistance. The composition exhibits a flexural modulus of at least 1500 megapascals, measured at 23 degrees C and a sample thickness of 3.2 mm in accordance with ASTM D 790-10. Moreover, in addition to having a good balance of the properties, the compositions have the necessary degree of stiffness to make them ideally suited for use in rigid articles. The composition exhibits a flame retardancy performance class of V-0 at a sample thickness of at most 1.5 mm, measured according to Underwriter's Laboratory Bulletin 94 Tests for Flammability of Plastic Materials, UL 94, 20 mm Vertical Burning Test, and at least two of the following properties: a notched Izod impact strength of at least 150 joules per meter, measured between -30 degrees C and -40 degrees C using a pendulum energy of 2.7 joules and an impact velocity of 3.5 m/second according to ASTM D 256-10; a melt mass-flow rate of at least 5 g/10 minutes, measured at 300 degrees C, a dwell time of 375 seconds, and a load of 5 kilograms according to ASTM D 1238-10, Procedure B; and a heat deflection temperature of at least 105 degrees C, measured at a sample thickness of 3.2 mm and a stress of 1.82 megapascals according to ASTM D 648-07. The composition exhibits a flexural modulus of at least 2000 megapascals, measured at 23 degrees C and a sample thickness of 3.2 mm in accordance with ASTM D 790-10.    DETAILED DESCRIPTION - A composition (C1) comprises (wt.%): a styrenic polymer (1-40) selected from rubber-modified polystyrenes, unhydrogenated block copolymers of an alkenyl aromatic compound and a conjugated diene, and/or hydrogenated block copolymers of an alkenyl aromatic compound and a conjugated diene; flame retardant (1-40) comprising an organophosphate ester; and poly(arylene ether)-polysiloxane block copolymer reaction product (greater than 55-95) comprising a poly(arylene ether) homopolymer, and a poly(arylene ether)-polysiloxane block copolymer comprising a poly(arylene ether) block, and a polysiloxane block comprising, on average, siloxane repeating units (20-80). The poly(arylene ether)-polysiloxane block copolymer reaction product comprises (wt.%): siloxane repeating units (1-30) and arylene ether repeating units (70-99); and the poly(arylene ether)-polysiloxane block copolymer reaction product is the product of a process by oxidatively copolymerizing a monomer mixture comprising a monohydric phenol and a hydroxyaryl-terminated polysiloxane; and the poly(arylene ether)-polysiloxane block copolymer reaction product has a weight average molecular weight of at least 30000 atomic mass units. An INDEPENDENT CLAIM is included for an injection molded article comprising the composition (C1).