Walmart is hosting a sale. Customers choose a random ticket that is takes 5%, 15%, or 25% off their total purchase. Ten percent of the tickets are labeled 25%, Twenty percent are labeled 15%, and the remaining are labeled 5%. What is the expected actual sale for a customer wishing to purchase $100 worth of merchandise?

Here's my work and answer: $75(.10) + $85(.20) + $95(.70) = $118.8

There's one more problem I need help with

The weight for a population of animal species follows a normal distribution. It is determined that 10% weights exceed 12.513, and 1% of the weights exceed 12.930. What are the mean and standard deviation of this population of battery voltages?

This one I'm not sure about. I tried looking at the normal curve and appying the 68-95-99.7, but that didn't work cause it wasn't even. I think I'm supposed to divide the differences or something?

Any help is appreciated :]