The return on the Rush Corporation in the state of recession is estimated to be $-24\%$ and the return on Rush in the state of boom is estimated to be $35\%.$ The return on the Oberman Corporation in the state of recession is estimated to be $41\%$ and the return on Oberman in the state of boom is estimated to be $-15\%.$ Given this information, what is the covariance between Rush and Oberman if there is a $0\mathrm{.}50$ probability that the economy will be in the state of boom and a $0\mathrm{.}50$ probability that the economy will be in the state of recession.