a)$ |h(x)| \leq (\int |f(x-y)|^p dy)^{1/p}(\int |g(y)|^q dy)^{1/q} = (\int |f(z)|^p dz)^{1/p}(\int |g(y)|^q dy)^{1/q} \leq ||f||_{p}||g||_{q} $
