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Given the following data of prestressed rectangular beam

Beam dimension; $bh=300mm600mm$

Loads; Super imposed deadload $=5k\frac{N}{m},$ Live load $=15k\frac{N}{m}$

Unit weight of concrete $=23k\frac{N}{m^3}$

Simple supported beam with a span of $12m$

Initial Presstressed $=1750kN$

Eccentricity $=220mm$

Presstress loss at service load $=15\%$

a$)$ Calculate the stress at bottom fiber at end span due to initial presttressing only

b$)$ Calculate the stress at the top fiber of the beam at midspan due to the service loads and prestressing force$($loss of presstress is $15\%)$

c$)$ Calculate the maximum additional uniform load that the beam can be subjected without producing tensile stress in conrete