Hi, could anyone help me with this problem?

A 10uF capacitor is charged at 300v and then discharged through a 5Kohm resistor. The voltage at any time, t is given by the equation

V = Vo e^ - t/rc (- is common to the whole fraction t/rc)

where Vo is the initial voltage, R is the resistance and C the capacitance.
a) Find the voltage at 5ms and 100ms
b)Find the time at which the voltage is 50v.

Any help appreciated thanks.