$3\mathrm{.}1$ The formula $,y=\frac{2F{L}^3}{27EI}$

is used to determine the midpoint deflection of a tubular composite shaft $($shown below$),$ where:

F: applied force $N$

L: support point distance $mm$

E: Elasticity of material $,\frac{v}{m^2}$

I: cross sectional moment of inertia

If the force $($F$)$ is increased by $0\mathrm{.}2\%$ and the support point distance $(L)$ is increased by $0\mathrm{.}5\%,$ use the partial differentiation method to approximate the percentage change in the midpoint deflection $(y).$

$(6)$