How do I compute my initial investment amount for my T-bills based on the cut-off yield?

T-bills are issued at a discount to the face value.

The cut-off yield at an auction determines the cut-off price of the T-bills, based on the formula below:
D = M/365 X R
P = S$100 – D

Where:
D = full discount per S$100 face value
M = days to maturity
R = annual rate of discount (yield), expressed as %
P = dollar price per S$100 face value

For example, if the cut-off yield for a 6-month T-bills with 182 days to maturity is 4.00%, this translates to a cut-off price of S$98.005 (rounded to 3 decimal places) per S$100 in face value. This means that for every S$1,000 of T-bills that was allotted to you, your initial investment amount would be S$980.05.