15 When deciding whether to open light in fourth position or pass the hand out (which avoids a negative score), count the number of high card points plus the number of spades. If the sum is ≥ 15, open.

This relies on the principle that if you control the spade suit opponents will not likely out bid you. So, open:

SJ852 H AQ7 D KJ84 C94

And pass out:
S852 H AQJ7 D KJ84 C94