My question is as follows: Speed driven by motorists are normally distributed with mean 63 and standard deviation unknown.

1.) If 2.5% of all motorists are traveling at speed 70 or more, what is the value for standard deviation?

2.) Mean and standard deviation are unknown. It is observed that 10% of all motorists travel at less than speed 36 and 10% of all motorists travel at more than speed 70. What must mean and standard deviation be?