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A post-tensioned concrete member of span $15 \; \text(m)$ and cross-section of $450 \; \text{mm} \times 450 \; \text{mm}$ is prestressed with three steel tendons, each of cross-sectional area $200 \; \text{mm}^{2}.$ The tendons are tensioned one after another to a stress of $1500 \; \text{MPa}.$ All the tendons are straight and located at $125 \; \text{mm}$ from the bottom of the member. Assume the prestress to be the same in all tendons and the modular ratio to be $6.$ The average loss of prestress, due to elastic deformation of concrete, considering all three tendons is

- $14.16 \; \text{MPa}$
- $7.08 \; \text{MPa}$
- $28.32 \; \text{MPa}$
- $42.48 \; \text{MPa}$