The chemical element einsteinium-$253$ naturally loses its mass over time. When a sample of einsteinium-$253$ was initially measured, it had a mass of $15$ grams.
The relationship between the elapsed time $t$, in weeks, and the mass, $M_{\text{week}}(t)$, left in the sample is modeled by the following function:
###$M_{\text{week}}(t)=15\cdot \left(0.79\right)\^{\Large t}$
**Complete the following sentence about the *daily* rate of change in the mass of the sample.**
*Round your answer to two decimal places.*
Every ***day***, the mass of the sample decays by a factor of [[☃ numeric-input 1]].