Geoffrey believes that the overall benefit from this agreement amounts to $355.82922901913 per week in arrears (this would include money he would have spent on alternative delivery services, estimated additional profits from using Gillian's services, etc).

By considering only the initial cost of $70,000 and this weekly benefit of $355.82922901913, calculate the interest rate that represents the return on this investment, expressed as a nominal annual rate compounding weekly.