The following table shows the joint and marginal distributions of the random variables X and Y, where X is the number of years of study completed by the head of the family and Y is the income stratum of the head of the family (according to times the salary overall minimum).

2 4 5 199 .124 . 122 005 .450 X 177 .035 .009 .003 ba wo .223 008 .025 .040 .049 065 187 .002 005 .022 .041 .071 .141 .386 . 188 . 193 098 .136