This question is maybe not just about evaluating whether investment y is profitable in terms of expected return vs. required return but you also may need to consider the opportunity cost, meaning, whether it makes more sense to invest in investment x or y plus whether it may be most beneficial to diversify into investments in x and y.
Without knowing the context in which the question was posed I would say that the answer is supposed to be qualitative in nature and that the correct answer should be that there is missing information in order to fully determine whether a diversification benefit will cause the best investment to be a portfolio of x and y. For example, details on the individuals' risk is only given as betas but the betas are computed through the covariance and individual investment's standard deviation, both of which are missing.
If the two investments are perfectly positively correlated then you would obviously want to invest everything in the investment with the most attractive expected return relative to the required return, but if the investments correlate otherwise then I would say that to give a precise answer you would need more information than what was given.
In summary, either the question looks for a purely qualitative answer and checks whether you understand the bigger picture of investing in different assets or you are simply asked to calculate the expected return of investment x through b1, r-f-rate, and market risk premium and compare with investment y. I would err on the former.