Struggling with physics problem

Question

A 30.0 μF capacitor initially charged to 30.0 μC is discharged through a 2.80 kΩ resistor. How long does it take to reduce the capacitor's charge to 15.0 μC?

my answers, 0.37, 0.12, and 0.58 were all incorrect.

Answer 1

We have to use capacitor's discharging formula, that is:

=> Q(t) = Qo (e^ -t / RC)

By plugging the given values in this equation and doing a bit of calculations, we will get

=> 0. 5 = e^(-t/84 * 10^-3)

taking the natural log on both side and solving the equation for 't', we will get

t = 0.058 sec.