Parameters
$d$	district where IMW generation center c is located
$Po{p}_d$	total population in district d
$Pop{M}_d$	total population of medical staff in district d
$Pop{C}_d$	the number of confirmed cases in district d
$W_{PPE}$	average PPE’ s weight per worker
$W_{test}$	the weight of items for one COVID-19 test
$W_{MW}$	the weight of basic IMW, such as masks per person, before outbreak
$W_{cure}$	the weight of IMW produced by treating an infected patient
$R_{PPE}$	acceptance rate of PPE before outbreak
$R{O}_{PPE}$	acceptance rate of PPE after outbreak
$R_{test}$	acceptance rate of COVID-19 tests before outbreak
$R{O}_{test}$	acceptance rate of COVID-19 tests after outbreak
$B_d^t$	1 if district d breaks out the pandemic, 0 otherwise