A 55-Kg Person Exposed to Thorium-234 Receives 7 $\beta$ Particles, Each with an Energy of 1

A 55-kg person exposed to thorium-234 receives 7.5 × 10⁴ $\beta$ particles, each with an energy of 1.6 × 10^-14 J. How many rads does the person receive?

A) 2.1 × 10^-19
B) 1.2 × 10^-17
C) 2.2 × 10^-9
D) 1.2 × 10^-9
E) none of the above