Clear SharePoint People Picker Value and enable button when people picker is not empty

Hi, i am using SharePoint client people picker in my application, i would like to

1. clear SharePoint People picker value on button click(i can able to clear all  fields text boxs, dropdowns and datetime, but not people picker).

2. i am disabling button at page load, how to enable button when i enter same people picker value. code using for people picker

<SharePoint:ClientPeoplePicker  Required="true" Localizable="false" ValidationEnabled="true" ID="ClientPeoplePickerEB" runat="server" VisibleSuggestions="3" Rows="1" AllowMultipleEntities="true" PrincipalAccountType="User,SPGroup,SecGroup,DL" AllowEmailAddresses="true" CssClass="ms-long ms-spellcheck-true" Width ="305px"  Height="70px"/>