title: How to calculate the sum of week hours?
body: <p>How can I calculate the sum of week hours?</p>
  
  <p>I have a Campus document like this,</p>
  
  <pre><code>{
      "_id" : ObjectId("5ce3beecf32c6e5ba2d767e8"),
      "managers" : [ 
          ObjectId("5cd2a3de1e2d5928b04321b9"), 
          ObjectId("5cd2a34e1e2d5928b04321b7")
      ],
      "admins" : [ 
          ObjectId("5cd3b1d0877c5b07921932dd")
      ],
      "status" : true,
      "name" : "Halliday Hall",
      "address1" : "Oliver Rd",
      "address2" : "Thunder Bay",
      "city" : "Ontario",
      "state" : "Ontario",
      "postCode" : "8465",
      "email" : "halliday@gmail.com",
      "phone" : 8475963269.0,
      "workingDays" : {
          "Sunday" : [ 
              "Closed", 
              "Closed"
          ],
          "Monday" : [ 
              "10:30 AM", 
              "04:30 PM"
          ],
          "Tuesday" : [ 
              "10:00 AM", 
              "05:00 PM"
          ],
          "Wednesday" : [ 
              "Closed", 
              "Closed"
          ],
          "Thursday" : [ 
              "Closed", 
              "Closed"
          ],
          "Friday" : [ 
              "Closed", 
              "Closed"
          ],
          "Saturday" : [ 
              "Closed", 
              "Closed"
          ]
      }
  }
  </code></pre>
  
  <p>wokingDays is of type Map</p>
  
  <pre><code>workingDays: {
              type: Map,
              of: Array
          }
  </code></pre>
  
  <p>All I want to do is calculate the sum of workings hours</p>
  
  <p>I tried using moment but was getting stuck with the query.</p>
  
  <p>The expected sum in this case would be 13 hrs.</p>