Phil bought a car by taking out a loan for $$\$ 18,500$$ at $0.5 \%$ interest per month. Phil's normal monthly payment is $$\$ 434.47$$ per month, but he decides that he can afford to pay $$\$ 100$$ extra toward the balance each month. His balance each month is given by the recursively defined sequence
$$
B_0=18,500 \quad B_n=1.005 B_{n-1}-534.47
$$
Determine Phil's balance after making the first payment. That is, determine $B_1$.