Let \( \vec a=4\hat i-\hat j+3\hat k \), \( \vec b=10\hat i+2\hat j-\hat k \) and a vector \( \vec c \) be such that \( 2(\vec a\times \vec b)+3(\vec b\times \vec c)=\vec 0 \). If \( \vec a\cdot \vec c=15 \), then \( \vec c\cdot(\hat i+\hat j-3\hat k) \) is equal to:
