Help please I'm desperate

I have been given this question for a tut but am unsure of how to answer it as it doesnt seem to have enough information for me, any help is greatly appreciated:

A company that markets user assembled furniture sells a computer desk that is advertised with the claim "less than an hour to assemble". However, through postpurchase surveys the company has learned that only 25% of their customers succeeded in building the desk in under an hour; 5% said it took them over 2 hours.

(a)Using this information and assuming that the desk assembly time follows the normal probability model, show that the mean and the standard deviation for the assembly time are 77.45 and 25.87 minutes respectively.

Probability is not a strong point for me

thanks