Explanation:

A decrease in tax shifts IS outward, increasing interest rate. This correspond to an outward shift in the AD, increasing price and output. Expected price changes in the medium run, and in particular, workers revise expected price upward following the price rise; this leads AS to contract over time, eventually intersecting AD at the natural level of output. As AS contracts, price increases, resulting in lower real money supply. As such, LM also contract over time, eventually intersecting IS at natural level of output. IS expanding + LM contracting both results in an increase in interest rate.