‘P’ is the pre-stressed force applied to the tendon of a rectangular pre-stressed beam whose area of cross section is ‘A’ and sectional modulus is ‘Z’. The maximum stress ‘f’ in the beam, subjected to a maximum bending moment ‘M’, is

• A. f = (P/'+ (Z/M)
• B. f = (A/P) + (M/Z)
• C. f = (P/A) + (M/Z)
• D. f = (P/A) + (M/6Z)