Calculate the expressions and give the answers to three significant figures when [[$ a= \text{1,2}, b=-\text{3,4}$]] and [[$c=-\text{5,6}$]].

a) [[$2a^7 =$]]

b) [[$(abc)^3 =$]]

c) [[$\left(a+\dfrac{c}{b}\right)^{10} =$]]