4) D

P = 2r²t


P = 2 (3 x 10⁻³)² (2.5 x 10⁴)


P = 2 (9 x 10⁻⁶) (2.5 x 10⁴)


P = 5 x 10⁴ x 9 x 10⁻⁶


P = 45 x 10⁻²


P = 4.5 x 10⁻¹