What is the effective resistance across this capacitor?

Question

A 0.02 microF capacitor is given a charge Q0. After 15 s, the capacitor's charge is 0.5Q0. What is the effective resistance across this capacitor? Answer in units of M­.

Answer 1

"Answer in units of M" huh?  Resistors are in ohms.

Charge goes to half, voltage also goes to half

v = v₀[1 - e^(-t/RC)]

v/v₀ = 1 - e^(-t/RC)

0.5 = 1 - e^(-15/R(0.02uF))

0.5 = e^(-15/R(0.02uF))

ln of both sides

-0.693 = -15/R(0.02uF)

15*R*0.02uF = 0.693

R = 0.222 Mohm or 222 kohm