The Martingale Doubling System on Roulette

On a roulette red bet you win (even money) with probability $18/38$ and lose with probability $20/38$. You run the doubling (martingale) system aiming to win $\$1$: bet $\$1$; if it loses, bet $\$2$; if that loses, bet $\$4$. You stop after a win or after three straight losses (your bankroll of $\$7$ is then gone). Find (a) the probability the campaign ends in ruin and (b) the expected net profit of the campaign.