The working stress method of design specifies the value of modular ratio, $$m = 280/\left( {3{\sigma _{cbc}}} \right),$$ where $${{\sigma _{cbc}}}$$ is the allowable stress in bending compression in concrete. To what extent does the above value of $$'m'$$ make any allowance for the creep of concrete?

The following two statements are made with reference to a simply supported under - reinforced $$RCC$$ beam:

$${\rm I}.\,\,\,\,\,\,\,\,\,\,\,\,$$ Failure takes place by crushing of concrete before the steel has yielded.
$${\rm II}.\,\,\,\,\,\,\,\,\,\,$$ The neutral axis moves up as the load is increased.

With reference to the above statements, which of the following applies?

Assume straight line instead of parabola for stress-strain curve of concrete as given below and partial factor of safety as $$1.0.$$

A rectangular under-reinforced concrete section of $$300$$ $$mm$$ width and $$500$$ $$mm$$ effective depth is reinforced with $$3$$ bars of grade $$Fe$$-$$415,$$ each of $$16$$ $$mm$$ diameter. Concrete mix is $$M20.$$

The depth of the neutral axis from the compression fibre is

Assume straight line instead of parabola for stress-strain curve of concrete as given below and partial factor of safety as $$1.0.$$

A rectangular under-reinforced concrete section of $$300$$ $$mm$$ width and $$500$$ $$mm$$ effective depth is reinforced with $$3$$ bars of grade $$Fe$$-$$415,$$ each of $$16$$ $$mm$$ diameter. Concrete mix is $$M20.$$

The depth of the neutral axis obtained as per $$IS:$$ $$456$$-$$2000$$ differs from the depth of neutral axis obtained in $$Q.08$$ by