How construct PDA to $L = \{x \in(a,b,c,d)^* \mid -10 \leq ( |x|_a + |x|_b) - ( |x|_c + |x|_d) \leq 10 \}$

Question

$L = \{x \in(a,b,c,d)^* \mid -10 \leq ( |x|_a + |x|_b) - ( |x|_c + |x|_d) \leq 10 \}$

I don't have any idea. Can someone help me.

Answer 1

If anyone would be interested, here is my pda to $L = \{x \in(a,b,c,d)^* \mid -1 \leq ( |x|_a + |x|_b) - ( |x|_c + |x|_d) \leq 1 \}$