If R is the total resistance of three resistors, connected in parallel, with resistances R1 , R2 , R3 , then 1/R=1/R1+1/R2+1/R3 If the resistances are measured in ohms as R1=25ohm, R2=40ohm and R3=50ohm , with a possible error of0.5% in each case, estimate the maximum error in the calculated value of R.