Let's assume that the current price is R, and the due payment amount of the voucher is 1000*( 1+6%). According to the income under the market interest rate, there are:

1000 *( 1+6%)-R = R * 8% * 3/ 12

r = 1000 *( 1+6%)/(8% * 3/ 12+ 1)= 1039.22