good evening tutor, if it's not too much stress could you explain how you solved for each bullet point

A continuous RV, x has probability distribution function (PDF) defined as follows: fx(x) = (ax + b) for OsXsu = 0 otherwise where a and b are arbitrary constants. Further, the first moment of the RV, m1 = k. Find the following, if u = 5.6 and m1 = k = 2.25. Determine: . Coefficients, a and b in terms of u and k . Second moment of the RV, m2 . Standard deviation of the RV . CDF of the RV in the range 0 to x, Px(X)Multiple-choice Answers: Choose the Correct Result k I II III iv 1 0.041, - 0.068 13.30 2.902 - (3x92 + bx) 2 0.037, - 0.072 13.43 2.828 (ax2X2 + bx) 3 0.038, + 0.069 13.43 2.902 (ax2/2 + bx) 4 0.036, - 0.068 13.33 2.329 (ax2X2 - bx) 5 0.038, + 0.073 13.53 2.910 (ax2/2 + bx) 0 Choice 1 0 Choice 2 0 Choice 3 0 Choice 4 0 Choice 5