Actually come to think about it, if your goal is just to get the most out of your credits and you don't plan on using Azure for anything else, then you might as well create a VM with the 4x Tesla P100 GPU's or wait for the upcoming 4x Tesla V100 (more performance, but cheaper) VM's. Your credits will last you close to a day but you'll make more money in that day than you will mining within budget for a month. And then after that, you'll still have 750 hours of the very low end B1S VM that'll give you a little bit more hash power to whatever pre existing hashpower you already have.