Welcome starfox! I agree with Frixxxx about the F-fund. Bond charts are not setting up very well here. FWM gave you some good investment approach advice.
I will add to JTH's comment about the S&P 500 - most of us chart the S&P rather than the C fund as JTH said, so finding upside targets may be easier that way. But rather than picking a target, watching the charts for tehnical breakdowns might work better. That won't limit your upside if the market keeps moving higher, but once the C-fund hits your $15 target, you might consider a mental stop saying you will sell if it moves back to or below $15. Then you can raise that mental stop as prices keep rising.
Thanks for joining us and good luck!