For each of the following cases, indicate $($a$)$ what interest rate columns and $($b$)$ what number of periods you would refer to in looking up the discount rate.

$(1)$ In Table $3($present value of $1)$:

$($a$)$

$($b$)$

Case A

$\%$

periods

Case B

$\%$

periods

Case C

$\%$

periods