On March 1, 2020, the gold spot price was $1100/oz and 5-month Futures price was $1200/oz. The term structure of interest rates was flat (i.e., all zero rates were the same). During 1 month (from March 1st to April 1st), the spot price increased to $1115 while the Futures price on this contract decreased to $1190. On April 1st, the interest rate structure was flat as well. The size of the futures contract is 1oz and futures prices are always equal to forward prices.

If R1 is the interest rate on March 1, 2020 while R2 is the interest rate on April 1, 2020, what is (R1- R2)?