"A training program requires a pilot to fly circuits of an airfield. Each day, the pilot flies 4 more circuits than the previous day. On the third day, the pilot flew 10 circuits. The number of circuits the pilot flew in total by the end of the 6th day was _____."

This question is in regards to arithmetic sequences/series, but I'm not sure what exactly the known variables are in order to solve. Please be thorough in any explanations.