GemTech sold equipment that provided $$15$ thousand in initial contribution and $$2$ thousand in annual contribution for $2$ years $($with payments at year end$).$ The customer attrition from year $1$ to $2$ was $5\%.$ The discount rate was $20\%.$

GemTech's marketing strategy was to use Google Ads. The company paid $$5$ thousand to Google Ads to achieve one sale.

What was the company's lifetime value to customer acquisition cost ratio? The correct answer is $3\mathrm{.}6,$ please explain fully