calculate t he reliability of t he system. Solution reliability of the system= let 1 and 2 are the system and their equivalent reliability(parallel) = 1- (1-R1)(1-R2) = 1-(-R1-R2+R1R2+1) = R1+R2-R1R2---------- eq.1 let 3 and 4 are are the system and their equivalent reliability(parallel)= 1- (1-R3)(1-R4) = 1-(-R3- R4+R3R4+1) = R3+R4- R3R4--------eq.2 both eq.1 and eq.2 are in series net reliability of the total system =(R1+R2-R1R2)(R3+R4- R3R4).