设overrightarrow(a)=(1,1,4),overrightarrow(b)=(1,-2,2),则overrightarrow(a)+overrightarrow(b)在overrightarrow(a)方向上的投影为( )

A. $\frac{7}{2}$

B. $\frac{25}{3\sqrt{2}}$

C. 3$\sqrt{2}$

D. $\frac{6}{3\sqrt{2}}$

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