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

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