Question 1042236
I'll give it a try:
{{{ p(t) = 250 - 120*2.8^(-5t) }}}
{{{ p(4) = 250 - 120*2.8^(-.5*4) }}}
{{{ p(4) = 250 - 120*2.8^(-2) }}}
{{{ p(4) = 250 - 120*.12755 }}}
{{{ p(4) = 250 - 15.306 }}}
{{{ p(4) = 234.694 }}} symbols/min
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check:
Here's the plot:
{{{ graph( 400, 400, -10, 20, -25, 300, 250 - 120*2.8^(-.5x) ) }}}
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Not sure where your problem is.
{{{ p(t) }}} is positive for all {{{ t >= 0 }}}
Note that {{{ 2.8^(-2) = 1 / ( 2.8^2 ) }}}