Answer:
i got c
Explanation:
I think it is D but don't count on it
t=360S
T½=2mins
No=60x10^6
t=?
Nr=7.5x10^6
Nr/No=1/2^n
7.5x10^6/60x10^6=(1/2)^n
0.125=2^- n
Take log to bothsides
Log10^0.125=log10^2^- n
Ln0.125= -nln2
- 2.079= - 0.693n
N=2.079/0.693
N=3
N=t/T
t=nxT
t=3x2x60
t=360s