如图所示,在平行六面体ABCD-A
1B
1C
1D
1中,设\( \overrightarrow {AA_{1}}= \overrightarrow {a}\),\( \overrightarrow {AB}= \overrightarrow {b}\),\( \overrightarrow {AD}= \overrightarrow {c}\),M,N,P分别是AA
1,BC,C
1D
1的中点,则\( \overrightarrow {MP}+ \overrightarrow {NC_{1}}\)=( )