A system starts working at time \(t=0\). Its lifetime has approximately a normal distribution with mean value \(\mu=125\) hours and standard deviation \(\sigma=40\) hours. After a failure, the system is replaced with an equivalent new one in negligible time, and it immediately takes up its work. All system lifetimes are independent.

(1) What is the minimal number of systems, which must be available, in order to be able to maintain the replacement process over an interval of length 500 hours with probability 0.99 ?

(2) Solve the same problem on condition that the system lifetime has an exponential distribution with mean value \(\mu=125\).