Please help me with these questions!!

The brain volumes (cm cubed) of 50 brains vary from a low of 904 cm cubed to a high of 1488 cm cubed. use the range rule of thumb to estimate the standard deviation s and compare the result to the exact standard deviation of 175.5 cm cubed, assuming the estimate is accurate if it is within 15 cm cubed

True or false: the graph of y=f(bx) is a horizontal compression of the graph y=f(x) if b< 1

In the equation sqrt(n+5)-sqrt(11-10)=1. what is the value of n