$($ Fixed Income Securities$)18)$ F$)$ Define the curvature of the term structure with respect to short$-$term, medium$-$term and long$-$term bonds and hence calculate the curvatures of the term structure at time t and time t$+1$ using the table below

Term structure of interest rates

Maturity Time t Time t$+1$

Short$-$term $3\%2\%$

Medium$-$term $4\%5\%$

Long$-$term $5\%4\%$