Correlation coefficient by change of rate of return

[rragas]

Every time a certain asset A sees a 1 percent jump in rate of return, the return on asset B sees exactly a 0.5 percent decrease (with no error). What is the correlation coefficient between the returns of these two assets?

 

[tutor_joel]

I'm not sure how to approach this. Perhaps you could elaborate a bit more. Are there certain equations that you use?