The city of Berkeley will require medical marijuana dispensaries to give away two percent of the amount of cannabis they sell each year free to low-income patients. The City Council voted unanimously at Tuesday’s meeting to amend the city’s medical pot rules, which would also allow for a fourth dispensary in Berkeley. Under the proposal, at least two percent of all medical weed dispensed at a club would have to be provided at no cost to very low-income members — and it must be the same quality that’s dispensed to regular paying customers.