Consider the following table for an eight$-$year period:

$\backslash$table$[[$Year$,$T$-$bill return,Inflation$],[1,7\mathrm{.}40\%,8\mathrm{.}60\%],[2,8\mathrm{.}59,12\mathrm{.}23],[3,5\mathrm{.}98,6\mathrm{.}83],[4,5\mathrm{.}62,4\mathrm{.}97],[5,5\mathrm{.}56,6\mathrm{.}59],[6,8\mathrm{.}19,8\mathrm{.}91],[7,10\mathrm{.}67,13\mathrm{.}18],[8,12\mathrm{.}65,12\mathrm{.}41]]$

a$.$ Calculate the average return for Treasury bills and the average annual inflation rate $($consumer price index$)$ for this period.

Note: Do not round intermediate calculations and enter your answers as a percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.$

b$.$ Calculate the standard deviation of Treasury bill returns and inflation over this time period.

Note: Do not round intermediate calculations and enter your answers as a percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.$

c$.$ Calculate the real return for each year."$8"$

Note: A negative answer should be indicated by a minus sign. Leave no cells blank $-$ be certain to enter $"O^{\text{'}\text{'}}$ wherever required. Do not round intermediate calculations and enter your answers as a percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.$

d$.$ What is the average real return for Treasury bills?

Note: A negative answer should be indicated by a minus sign. Do not round intermediate calculations and enter your answer as a percent rounded to $2$ decimal places, e$.$g$.,32\mathrm{.}16.$