(7) | Cash and cash equivalents |
| | December 31, | | |||||||
| | 2017 | | 2016 | | 2015 | | |||
Cash and banks | | $ | 15,464,312 | | | 9,890,007 | | | 4,774,420 | |
Investments with maturities less than three months | | | 623,898 | | | 4,771,961 | | | 9,246,071 | |
Cash and cash equivalents | | | 16,088,210 | | | 14,661,968 | | | 14,020,491 | |
Restricted cash | | | 24,058 | | | 19,236 | | | 25,771 | |
Total cash and cash equivalents and restricted cash | | $ | 16,112,268 | | | 14,681,204 | | | 14,046,262 | |