3.7 the total number of hours, measured in units of 100 hours, that a family runs a vacuum cleaner over a period of one year is a continuous random variable x that has the density function
f(x)=⎧ x,0< x< 1
2−x, 1 ≤ x< 2,
0, elsewhere.
find the probability that over a period of one year, a family runs their vacuum cleaner (a) less than 120 hours; (b) between 50 and 100 hours