Every day you double your capital so after d days you accumulate 2^d times your starting capital of 5c. When d=1 (the next day), your 5c becomes 10c. When d=10 your 5c becomes 1024*0.05=$51.20. When d=11, your capital doubles to $102.40. You'll be a millionaire after 25 days with $1,677,721.60 and a thrice billionaire after 36 days with $3.436B.