The mean value of a function f(x) from point ‘a’ to point ‘b’ is given by

• A. \(\frac{{f\left( a \right) + f\left( b \right)}}{2}\)
• B. \(\frac{{f\left( a \right) + 2f\left( {\frac{{a + b}}{2}} \right) + f\left( b \right)}}{4}\)
• C. \(\mathop \smallint \limits_a^b f\left( x \right)dx\)
• D. \(\frac{{\mathop \smallint \nolimits_a^b f\left( x \right)dx}}{{\left( {b - a} \right)}}\)