2.4. Among employees of a certain firm, 70% know C/C++. 60% know Fortran, and 50% know both languages. What portion of programmers (a) does not know Fortran? (b) does not know Fortran and does not know C/C++? (e) knows C/C++ but not Fortran? (d) knows Fortran but not C/C++? (e) If someone knows Fortran, what is the probability that he/she knows C/C++ too? (f) If someone knows C/C++, what is the probability that he/she knows Fortran too