‘P’ is the pre-stressed force applied to tendon of a rectangular pre-stressed beam whose area of cross section is ‘A’ and sectional modulus is ‘Z’. The minimum stress ‘f’ on 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)