Let P(x), Q(x) and R(x) be statements "x is a clear explanation", "x is satisfactory" and "x is an excuse" respectively. Suppose that the universe of discourse for x consists of all English test. Express the following statements using quantifiers, logical connectives and P(x), Q(x) and R(x)
a) All clear explanations are satisfactory
b) some excuses are satisfactory
c) some excuses are not clear explanations
d) does (c) follow from (a) and (b) ? (explain)