What is the basic assumption of the equation from which the coefficients of maximum bending moments per unit width in a slab are derived in Table $27$ of IS$-456$: $2000?$ How does it justify the expression for My in terms of lx$?$ What is the ratio of the central deflection for a unit strip, $1$m by $1$m spanning along ly and lx and why?$$ List the factors that would govern the provision of a corner grid two$-$way slab