how can I create Task and Event for a lead using Vtiger API

I use Vtiger Api to create a new lead. Now I need to create new Task or new Event for my lead.

who can help me? and has an example

this is my code:

{
    "operation":"create",
    "format":"json",
    "sessionName":"221747465d9f2d70a76e9",
    "elementType":"Leads",
    "element": {
        "firstname":"test",
        "lastname":"test", //mandatory
        "email":"[email protected]", 
        "phone":"123456789", 
        "country":"Oman", 
        "website":"https://test.com/", 
        //list of mandatory fields is unique to your crm
        "assigned_user_id":"19x97" // this is parameter from authorisation response    
    }  
}

I don’t have any idea…