The loudness of a sound changes. How much is the sound change in dB

The loudness of a sound changes. How much is the sound change in dB if
(a) the intensity increases tenfold?
(b) the intensity doubles?
(c) the amplitude doubles? (How is amplitude related to intensity?)
(d) the intensity decreases by 50%?
(e) the intensity increases 800%? (Hint: a 100% increase is the same as doubling; what is a 200% increase?
300%?)