If A is a square matrix of order 3 and det A = 5, then what is det {2 (A)^$$-$$1} equal to?

Let $$a{x^3} + b{x^2} + cx + d = \left| {\matrix{ {x - 1} & {2x} & {3x} \cr {2x + 3} & {x + 1} & x \cr {2 - x} & {3x + 4} & {5x - 1} \cr } } \right|$$

What is the value of c?

Let $$a{x^3} + b{x^2} + cx + d = \left| {\matrix{ {x - 1} & {2x} & {3x} \cr {2x + 3} & {x + 1} & x \cr {2 - x} & {3x + 4} & {5x - 1} \cr } } \right|$$

What is the value of a + b + c + d ?

If $$m = \left[ {\matrix{ 1 & 0 \cr 0 & 1 \cr } } \right]$$ and $$n = \left[ {\matrix{ 0 & 1 \cr { - 1} & 0 \cr } } \right]$$, then what is the value of the determinant of $$m\cos \theta $$ $$-$$ $$n\sin \theta $$ ?