What is the standard deviation of the exponential distribution whose density function is f(x)=10*e^(-10x)?

He ! a group of farmers planned to clean 80 acres of wheat per day to finish the work on schedule. right before the work started, they received a new piece of machinery that them clean 10 more acres per day than originally planned. as a result of increased productivity in the last day before the deadline they only had to clean 30 acres. how many acres of wheat did the group of farmers have to clean?

With number 11 ( show how you got the answer)

Ron has 8 caps and 4 of his caps are blue. thes rest of his cap are red. how many of ron's caps are red