Hi,

I've been asked the following question:

The temperature of an electrical device at a time 't' is given by the function:

Where is the temperature at time t = 0 and is a constant

Find a) when is 60 degrees Celsius, t = 50 seconds and = 90 seconds

b) The time t, for to be the value of

I believe the answer for (a) to be:

However for question (b) I've gotten:

Can someone please let me know if I've gotten these correct?

Seconds

Thanks.